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HelpTest Code CLZ Clozapine, Serum
Additional Codes
| Epic Ordering Code | LAB3040876 |
| NBS code | LBC03979 |
| Service code | 36877 |
Reporting Name
Clozapine, SSpecimen Type
Serum RedOrdering Guidance
Specimen Required
Supplies: Sarstedt Aliquot Tube, 5 mL (T914)
Collection Container/Tube: Red top (serum gel/SST are not acceptable)
Submission Container/Tube: Plastic vial
Specimen Volume: 1 mL
Collection Instructions:
1. Collect specimen immediately before next scheduled dose.
2. Within 2 hours of collection, centrifuge and aliquot serum into a plastic vial.
Additional Information: Therapeutic range (trough level) applies to specimens collected immediately prior to next dose.
NUH Outreach Laboratories:
Specimen Requirements
Submit the following:
Container: Red Top
Processing Requirements
Centrifuge and aliquot serum into a plastic vial within 2 hours
Specimen type: Serum
Volume: 1 mL
Storage/transport requirements: Refrigerated
Forms
If not ordering electronically, complete, print, and send a Therapeutics Test Request (T831) with the specimen.
Specimen Minimum Volume
0.6 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Serum Red | Refrigerated (preferred) | 28 days |
| Frozen | 28 days | |
| Ambient | 7 days |
Reject Due To
| Gross hemolysis | OK |
| Gross lipemia | OK |
| Gross icterus | OK |
Method Name
Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)
Day(s) Performed
Monday through Friday
Report Available
3 to 5 daysPlease note that this is a referral test requiring transport to the external testing facility and an additional 3-5 days is required.
Reference Values
Clozapine
Therapeutic range: 350-600 ng/mL
Norclozapine
Therapeutic range: Not well established
Clozapine + Norclozapine
Therapeutic range: Not well established
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Useful For
Monitoring patient compliance of clozapine treatment
An aid to achieving desired serum levels
CPT Code Information
80159
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| CLZ | Clozapine, S | 65632-2 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 33840 | Clozapine | 6896-5 |
| 33841 | Norclozapine | 10992-6 |
| 33842 | Clozapine+Norclozapine Total | 12375-2 |
Secondary ID
42366Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.Last updated 14/07/2026